Some existing tracking systems track an object having a radio frequency (RF) receiver within a transmission range of several RF transmitters. If, however, the object leaves the range of the RF transmitters, tracking cannot occur unless one adds more RF transmitters to expand the tracking region. Each newly added RF transmitter requires calibration to determine its position, an operation that can be tedious and time consuming.
Other tracking systems, such as GPS and cellular tracking, provide precise geo-location, but do not operate well indoors or in enclosed spaces (such as in a vehicle). GPS and cellular solutions also lack the accuracy required for certain applications.
Some wired tracking systems connect RF transmitters to a central controller and can synchronize the transmitters. Adding new RF transmitters to expand the tracking area, however, requires linking by wiring.
Centralized tracking systems have a central controller that typically controls when each RF transmitter is to transmit its RF signal. Systems having a central controller require reconfiguration when the system changes, such as adding or deleting a node. In contrast, decentralized systems that lack a central controller are exposed to the risk of multiple RF transmitters transmitting at the same time, potentially causing collisions between radio signals. During these collisions, part or all of a transmitted message may be lost.
Some existing wireless tracking systems require a central controller to handle the position calculation and networking functions. With these systems, an object being tracked transmits RF signals that are received by a plurality of RF receivers. The RF receivers are coupled to a central controller, which receives the signals, calculates the distance (range) from the RF transmitter to each RF receiver, and calculates the location of the RF transmitter in space. These systems encounter many trade-offs among important factors, such as power usage, position accuracy, cost, system control, and tracking range of the system.
In 2013, the Apple® Corporation of Cupertino Calif. introduced iBeacon™, a technology that uses low power Bluetooth® to transmit a beacon identifier to nearby electronic devices. The Meacon™ technology uses Bluetooth® low energy proximity sensing to determine the range to an electronic device (e.g., cell phone) passing near the beacon. Location-based actions (e.g., push advertising, check in) can then be activated by proximity detection. Such systems, however, are proximity detectors, not tracking systems. These proximity or range detection systems are interested in the registration of a wireless user, for purposes of communications and marketing.
In addition, wireless tracking systems in general suffer from RF interference that affects the received radio signal. If an RF transmitter and RF receiver are communicating on a narrow RF frequency band, and the RF interference is especially strong within this band, the signal can be obscured by the interference and measurements, and both position tracking and proximity detection, are affected.